Great Vowel Shift

From Conservapedia

The Great Vowel Shift was a massive sound change affecting the long vowels of English during the fifteenth to eighteenth centuries. The long vowels shifted upwards in pronunciation. For example, the word child went from being pronounced cheild to choild to the modern pronunciation. The word "she" was originally pronounced shay. There are many more examples and sound files to listen to at the webpage below. [1]